1. Field of the Invention
The present invention relates to a single-lens reflex camera in which a mirror can be retreated before a shutter is released.
2. Description of the Related Art
Conventionally, there is known a single-lens reflex camera, in which a mirror can be moved between an object observing position for observing an object through a view-finder and a photographing position for taking a picture of the object. When the mirror is set at the object observing position, the mirror is inclined so that a luminous flux passing through a photographing optical system is reflected by the mirror and led to the view-finder. When a shutter release is carried out, the mirror is rotated from the object observing position and retreated to the photographing position, in which the mirror is horizontally positioned. When the photographing operation is completed, the mirror is returned to the object observing position.
In the single-lens reflex camera, a photometry element is provided in an optical path of the view-finder in such a manner that a luminous flux, which is reflected by the mirror which is positioned at the object observing position, is led to the photometry element. A photometry value of the object is sensed, and based on the photometry value, a shutter speed and an aperture value are controlled so that a photographing operation is performed.
In a medium-size camera in which a film having a large photographing area, such as Browny film, is mounted, the mirror is large in proportion to the photographing area. Therefore, in a shutter release operation, a shock, caused by a movement and a stoppage when the mirror is rotated from the object observing position to the photographing position, may cause a bad influence on a photographed image. In order to prevent this influence, the camera is constructed in such a manner that the mirror can be retreated to the photographing position before the shutter release operation.
However, when the mirror is retreated to the photographing position before the shutter release operation, a photometry value of the object cannot be sensed by the photometry element provided in the optical path of the view-finder optical system. Therefore, a photographing operation must be carried out utilizing the photometry value of the object, sensed immediately before the mirror was retreated, with a shutter speed and an aperture value based on the photometry value. Therefore, if a significant change of a luminance of the object occurs after the mirror is retreated, the photographing operation cannot be properly performed.